1. Field of the Invention
The present invention relates to porcelain enamel frits and their use for the production of porcelain enamel coatings, especially for appliances, having improved cleanability to resist the adherence of food soils, i.e., baked on foods.
2. Description of the Prior Art
There are currently two practices used for the removal of food soils that have been baked on porcelain enamel surfaces, e.g., the interior of oven cavities. One approach is to pyrolize these coatings at elevated temperatures of approximately 500.degree. C. such that the food decomposes leaving a carbon ash residue that can be wiped off. However, this elevated temperature can be hazardous since one may easily be burned by touching the outside of an oven during the cleaning cycle. Furthermore, there is a tendency for porcelain enamels to craze and in some cases flake off when they are repeatedly exposed to such elevated temperatures leaving bare steel surfaces that may eventually rust. By eliminating the pyrolytic cleaning cycle from an oven, the associated safety hazards are avoided and a substantial cost savings is achieved which is beneficial to both the consumer and the manufacturer.
A second approach is to use a strong alkali cleaner having a very high pH (.congruent.12) combined with mechanical force to remove such baked on foods from porcelain enamel surfaces. This method is also disadvantageous because these highly alkaline cleaners are controversial and must be used with care.
It is an object of the present invention to provide porcelain enamel surfaces which do not require elevated temperatures or highly alkaline cleaners to remove baked on foods.
Surprisingly, it has been found that this object may be achieved in accordance with the present invention by preparing the porcelain enamel coatings from the frits to be described hereinafter.